In fact, had this man actually been a prisoner-of-war, he would not have been included in General Taylor's surrender agreement.

Prisoners-of-war were released from prison upon taking the oath of allegiance to the United States government. The only exception to this would be if the prisoner died, received an order for release from the President of the United States or the Secretary of War, or escaped from prison. Some prisoners were released by enlisting in Federal service, but an oath of allegiance was required here as well.